Typical balers comprise a frame pulled by a tractor over a field to pick up hay, straw or other crop to be baled and feeding the crop into a baling chamber where it is compressed into bales. One common baler type creates parallelepiped shaped bales that are formed by a plunger which reciprocates inside a baling chamber. When the bales are complete a tying mechanism is actuated to bind the bale before it is ejected from the baler.
Typically the plunger reciprocates in the baling chamber against the crop material when a new charge of crop is introduced into the chamber. Crop is fed into the baler via a crop pick-up assembly located at ground level and a duct communicating between the pick-up assembly and the baling chamber. Crop is typically pre-compressed in the duct prior to introduction into the baling chamber. A stuffer mechanism then transfers the pre-compressed crop into the baling chamber whenever enough crop material is made available in the duct.
There are four basic types of machine configurations possible with the plunger and stuffer combination. The first type has a continuous plunger, i.e. the plunger is gearbox driven and operates continuously, and a continuous stuffer. With this type of baler crop is continuously fed into a pre-compression chamber by e.g. a three cycle feed rake, each successive cycle filling the chamber and the third cycle moving the flake into the baling chamber where the plunger compresses the flake into a bale.
The second type of baler design also has a continuous plunger, but uses an intermittent stuffer. Here crop is fed into the pre-compression chamber to form a flake, the flake is then transferred into the baling chamber via an intermittently operating stuffer and then the plunger compresses the flake into the bale.
The third type of known baler design uses an intermittent plunger i.e. the plunger is not gearbox driven but is driven e.g. hydraulically and the stuffer is driven continuously. With this continuous feeding system there is no pre-compression chamber and the crop is delivered directly into the baling chamber via a feed fork. A switch at the top of the bale chamber activates a plunger cycle when the baling chamber fills with crop and exerts pressure on the switch.
The fourth and last type of known baler configuration also uses an intermittently driven plunger e.g. hydraulically driven, and also uses an intermittent stuffer. This type of system provides the greatest level of flake consistency as to size and density, because under ideal circumstances the intermittent plunger is always in the ready position when the signal is received that the pre-compression chamber is full. When the pre-compression chamber sensor indicates that sufficient crop has entered the pre-compression chamber a signal is sent to the intermittent stuffer which immediately begins to move the flake from the pre-compression chamber into the baling chamber. As the stuffer approaches a pre-determined position the plunger movement is started. The result is improved flake consistency. This combination gives the best bale quality by having consistent density from top to bottom (due to the intermittent feed system) and consistent flake sizes (from the intermittent plunger system).
In pending patent application Ser. No. 11/140,637 filed 27 May 2005 and assigned to the assignee of the present application a method is provided for determining the throughput of a parallelepiped agricultural baler. In this method a wait time between when the feed duct (pre-compression chamber) has reached a predetermined density for transfer of crop to the baling chamber and the plunger is in the home position is calculated and displayed to an operator of the baler, thereby allowing the operator to adjust the baler speed to attain maximum throughput. Such a method when used in conjunction with balers of the fourth type described above (intermittent plunger/intermittent stuffer) allows a baler operator to achieve highly consistent bales with respect to bale density and flake size.
It is desirable to measure crop yield as a crop is being baled so that the operator knows how many tons have been harvested from a field and to identify yield variability throughout the field. One proposed method for doing this involves weighing the total mass of a bale (via load cells) after the bale has been formed and correlating the incremental rotation of the star-wheel to field position to estimate crop yield variability. However, this method requires additional load cells and framework which adds to the cost of the baler. Further, incremental measuring wheels must be used to try to estimate the variation in yield as the bale is being formed which results in additional components and expense.
Accordingly, there is a clear need in the art for a method of determining crop yield without adding a great deal of additional structure and cost to the baler.